The present invention relates to the field of mass storage devices. More particularly, this invention relates to a method and apparatus for depositing a multiple layers on a storage disc.
One key component of any computer system is a device to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disc drive. The most basic parts of a disc drive are an information storage disc that is rotated, an actuator that moves a transducer to various locations over the disc, and electrical circuitry that is used to write and read data to and from the disc. The disc drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disc surface. A microprocessor controls most of the operations of the disc drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disc.
The transducer is typically placed on a small ceramic block, also referred to as a slider that is aerodynamically designed so that it flies over the disc. The slider is passed over the disc in a transducing relationship with the disc. Most sliders have an air-bearing surface (ABS), which includes rails and a cavity between the rails. When the disc rotates (generally, at rotational speeds of 10,000 RPM or higher), air is dragged between the rails and the disc surface causing pressure, which forces the head away from the disc. At the same time, the air rushing past the cavity or depression in the air-bearing surface produces a negative pressure area. The negative pressure or suction counteracts the pressure produced at the rails. The slider is also attached to a load spring, which produces a force on the slider directed toward the disc surface. The various forces on the slider equilibrate, so that the slider flies over the surface of the disc at a particular desired fly height. The fly height is the distance between the disc surface and the transducing head, which is typically the thickness of the air lubrication film. This film eliminates the friction and resulting wear that could occur if the transducing head and disc were in mechanical contact during disc rotation.
Information representative of data is stored on the surface of the memory disc. Disc drive systems read and write information stored on tracks on memory discs. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the memory disc, read and write information on the memory discs when the transducers are accurately positioned over one of the designated tracks on the surface of the memory disc. The transducer is also said to be moved to a target track. As the memory disc spins, the read/write head is accurately positioned above a target track and current is passed through the write head which in turn magnetizes a small area of the magnetic layer on the disc. The write head includes a coil of wire. Passing current through the write head results in a magnetic field in a gap near the surface of the disc. The magnetic field acts to magnetize a small area of the disc. This process is also known as writing information representative of data onto the memory disc. Similarly, reading data on a memory disc is accomplished by positioning the read/write head above a target track and reading the stored material on the memory disc.
The best performance of the disc drive results when the slider is flown as closely to the surface of the disc as possible. In operation, the distance between the slider and the disc is very small; currently xe2x80x9cflyxe2x80x9d heights or head media spacing is about 1-2 micro inches. It is contemplated that smaller fly heights or head media spacing will be achieved in the future since this is one factor in achieving increased recording density.
The constant demand for increasing hard drive recording density has resulted in drastic changes in disc drives over the years. One of the areas of change that has been necessary to increase the capacity of the disc drive is to place different types of magnetic layers onto the surface of the disc. Enhanced magnetic layers provide capacity since smaller and smaller portions of the magnetic layer and smaller portions of the disc surface are needed to store a xe2x80x9c1xe2x80x9d or a xe2x80x9c0xe2x80x9d(the information representing data). In other words, smaller magnetic layers are needed to define domains which must be flipped to store information representing data. One of the media enhancements includes a disc having as many as 30 alternating thin, metal layers such as Cobalt and Platinum. Each layer of material is from 5 to 8 Angstroms thick.
In the disc drive industry, high-performance, thin-film storage discs are generally produced by depositing successive layers on a substrate apparatus. For storage discs of the type formed on a rigid disc substrate, each successive layer on the storage disc is deposited in a separate chamber. Producing such a disc with a multiplicity of magnetic layer including as many as thirty thin layers alternating between Cobalt and Platinum using conventional sputtering devices would result in high capital costs and a lengthy process with a long throughput time. Producing such a disc would generally require many sputtering stations, one sputtering cobalt and the next sputtering platinum. The process would be long in terms of time since the disc would have to be moved many times into various chambers. The result is that there is not an efficient deposition process or sputtering apparatus that could deposit multiple very thin layers onto the surface of a disc. Therefore, there is a need for a method and apparatus that could be used to form multiple thin layers of alternating material onto a substrate surface.
A method for sputtering within a chamber includes the steps of placing at least two source materials within a chamber, electrically connecting a source of power to one of the source materials within the chamber to sputter a first layer onto a substrate, and disconnecting a source of power from one of the source materials and electrically connecting the source of power to the other of the source materials within the chamber to sputter a second layer onto a substrate. The method further includes the step of moving the substrate closer to the source connected to the source of power. Some embodiments further include the step of spinning the substrate within the chamber. The method may also include holding the substrate by an inner diameter within the chamber. The method for sputtering within a chamber also includes the step of alternately connecting power to one of the sources and then to another source to place a desired number of alternating layers of material on the substrate.
A sputtering apparatus for depositing layers of material onto a substrate includes a vacuum chamber, a first target and a second target positioned within the vacuum chamber. A source of power is placed in electrical communication with the first target and the second target. A switch alternately connects the source of power between the first target and the second target. The first target and the second target are different materials. The sputtering apparatus also includes a transport mechanism for moving a substrate between a first position closer to the first target and a second position closer to the second target. The switch connects power to the first target when the transport mechanism positions the substrate near the first target and the switch connects power to the second target when the transport mechanism positions the substrate closer to the second target. In one embodiment, the first target is ring-shaped and the second target is ring-shaped.
In other embodiments, the sputtering apparatus includes a third target and a fourth target. The first target, second target, third target, and fourth target are ring-shaped. The transport mechanism moves a substrate between a first position between the first target and the third target, and a second position between the second target and the fourth target. The first and third target are attached to the source of power when a substrate is positioned in a first position between the first and third target, and the second target and fourth target are attached to the source of power when a substrate is positioned in a second position between the second and fourth targets. The first target and third target are made of a first material. The second target and fourth target are made of a second material. The material of the first and third target is deposited on a substrate when in a first position, and the material of the second and fourth target are deposited on a substrate when in a second position.
The sputtering apparatus may handle a substrate that includes an inner diameter and an outer diameter. The transport mechanism for such a substrate includes a holder for holding a substrate by the inner diameter. The transport mechanism may also include a bellows for sealing the chamber when the substrate is placed in a first position and in a second position. In some embodiments, the sputtering apparatus for a substrate having an inner diameter and an outer diameter, includes a holder for holding a substrate by the inner diameter, a ram attached to the holder, and a bellows to seal the chamber and the transport mechanism. In some embodiments, the transport mechanism includes a rotator for rotating the substrate.
Most generally, a sputtering apparatus includes a chamber, and a device for sputtering layers of alternating material onto a substrate positioned within the chamber.
Advantageously, the method and apparatus described above provides a process which significantly reduces the process time necessary to place multiple layers of alternating material on a substrate.